1. Field of the Invention
This invention relates generally to erectors for use with a gyroscopic horizon or gyro vertical which uses a gyro to detect an inclination angle of a navigation vessel or vehicle such as ships and the like and transmit the corresponding signal. More particularly, the present invention relates to an erector by which when the spin axis of a gyro rotor used in the gyroscopic horizon is displaced from the vertical line, in accordance with the displaced amount of the spin axis, an erecting torque is applied so as to make the spin axis coincident with the vertical line.
2. Description of the Prior Art
FIG. 1 is a perspective view illustrating an outlined construction of an example of a prior art gyroscopic horizon to which this invention will be applied.
In FIG. 1, reference numeral 1 generally designates a gyro casing which incorporates therein a gyro rotor 2 the spin axis of which is substantially coincident with the vertical line and the gyro rotor 2 is rotated at high speed. Reference numeral 3 designates an erector which holds the spin axis of the gyro rotor 2 in substantially the vertical state. The gyro casing 1 is provided at its position perpendicular to the spin axis of the gyro rotor 2 with pitch shafts 4 and 4'. Reference numeral 5 designates a gimbal ring which is located in the outer periphery of the position of the gyro casing 1 as shown in the figure. The gimbal ring 5 has pitch axis bearings 6 and 6' with which the pitch shafts 4 and 4' are respectively engaged so that the gyro casing 1 is rotatably supported around the pitch shafts 4 and 4'. The gimbal ring 5 is provided at its position perpendicular to the pitch axis bearings 6 and 6' with roll shafts 7 and 7' and the roll shafts 7 and 7' are respectively engaged with roll axis bearings 9 and 9' provided in two bearing base plates 8 and 8' which are mounted on a base plate 10, whereby to rotatably support the gimbal ring 5 around the roll shafts 7 and 7'.
Reference numeral 11 designates a pitch angle transmitter which transmits to the outside a signal that corresponds to a rotation angle (that is, the pitch angle of the navigation vessel) of the gimbal ring 5 with respect to the gyro casing 1 around the pitch shafts 4 and 4'. Reference numeral 12 designates a roll angle transmitter which transmits to the outside a signal that corresponds to the rotation angle (that is, the roll angle of the navigation vessel) of the gimbal ring 5 with respect to the base plate 10 around the roll shafts 7 and 7'.
FIG. 2 is an enlarged cross-sectional view of an example of the prior art erector 3 shown in FIG. 1. As shown in FIG. 2, in accordance with this prior art example, a disc-shape magnet 3-1 of the erector 3 is engaged with the tip end portion of an extended portion 2-2 which, is attached to the upper portion of the shaft 2-1 of the gyro rotor 2. While, the gyro casing 1 is provided on its upper portion with an annular groove portion 1-1, and this gyro casing 1 is attached with a sun gear 3-2 having a boss 3-3 with which the inner ring of a bearing 3-4 is engaged. A rotation portion 3-5 of the erector 3 is pivotably supported by the outer ring of the above bearing 3-4 and has fixed thereto an annular ring 3-6 made of a good electrically conductive metal such as copper and the like in opposing relation to the magnet 3-1. A planetary gear 3-8 which is meshed with the sun gear 3-2 and a ratchet gear 3-9 are each coaxially fixed to a shaft 3-7 which is rotatably supported by the rotation portion 3-5.
FIG. 3 is a top view showing a main part of FIG. 2. As shown in FIG. 3, a ratchet member 3-10 is rotatably supported by the rotation portion 3-5 so as to intermittently engage with the ratchet wheel 3-9 and to thereby form a speed damper, namely, a speed governor mechanism section. As shown in FIG. 3, the rotation portion 3-5 has at its position opposite to the speed governor mechanism section two arms 3-11 and 3-12. The arm 3-11 is provided at its position contacting with a ball 3-15 a patch metal 3-13, while the other arm 3-12 is provided at its position contacting with the ball 3-15 a roller 3-14.
Since the magnet 3-1 is fixed to the extended portion 2-2 of the shaft 2-1 of the gyro rotor 2, the magnet 3-1 is rotated together with the gyro rotor 2 at high speed. While, since a torque caused by an eddy current which is produced by the cooperation of the annular ring 3-6 and the magnet 3-1 is applied to the rotation portion 3-5, this rotation portion 3-5 is rotated in the same direction as that of the gyro rotor 2, to tilt shaft 2-2. The rotation of the rotation portion 3-5 is transmitted through the sun gear 3-2 and the planet gear 3-8 to the ratchet gear 3-9 and the ratchet member 3-10 (the speed governor mechanism section) and applied with a damping torque corresponding to the rotation speed so that the rotation speed of the rotation portion 3-5 is held low and substantially constant.
FIG. 4 is a diagram in which the prior art erector 3 shown in FIGS. 2 and 3 is viewed from the above (the left and right-hand sides thereof are reversed relative to FIG. 3). In this case, the gyro casing 1 is inclined by an angle .theta. around X-X' axis in the figure. As shown in FIG. 4, when the ball 3-15 exists in the right-hand side half of Y-Y' axis, the slope is ascended so that the decelerating torque is produced by the weight of the ball 3-15. At this time, since the ball 3-15 is comes in contact with the patch metal 3-13 and given a drag force is produced thereby, the rotation speed of the rotation portion 3-5 becomes lowered.
On the other hand, when the ball 3-15 comes to the left-hand side half of the Y-Y' axis, the slope is descended so that the ball 3-15 is rolled by its weight within a movable range angle .phi..sub.0 of the ball 3-15 between the arms 3-11 and 3-12. When the ball 3-15 contacts with the roller 3-14, it is rotated together with the rotation portion 3-5 while in contact with the roller 3-14. In this case, due to the fact that the torque caused by the weight of the ball 3-15 acts so as to accelerate the rotation of the rotation portion 3-5; the ball 3-15 contacts with the roller 3-14 and hence its friction torque is made smaller as compared with that of the case in which the ball 3-15 exists in the right-hand side half of the Y-Y' axis; and that the movable range angle .phi..sub.0 is formed between the arms 3-11 and 3-12 and the ball 3-15 itself rotates without being substantial resistance, and the rotation speed of the ball 3-15 becomes higher than that of the case in which the ball 3-15 is located in the right-hand side half of the Y-Y' axis. In other words, since the duration of the period in which the ball 3-15 is located in the right-hand side half of the Y-Y' axis is made to be long by the inclination angle .theta. of the spin axis of the gyro rotor 2, and the torque as shown by T in FIG. 4 is produced. This torque T acts as the precession torque of the gyro so as to decrease the inclination of the spin axis so that the spin axis of the gyro rotor 2 is finally made coincident with the vertical line. Thus, the erector 3 performs its functions. However, the prior art erector 3 has the following shortcomings.
(1) In order to decelerate the rotation of the gyro rotor 2 that is rotated at high speed at about 10000 r.p.m. to a rotation low speed of about 1 to 20 r.p.m. and also to make its low speed rotation constant, the prior art erector 3 requires a plurality of special and expensive parts such as a torque transmission mechanism formed by the magnet 3-1 and the annular ring 3-6, the decelerating mechanism formed of the sun gear 3-2 and the planet gear 3-8, the speed governor mechanism formed of the ratchet gear 3-9 and the ratchet member 3-10. Further, it takes a long time for such parts to be assembled and to be adjusted.
(2) Since insufficient lubrication of the decelerating mechanism, the speed governor mechanism and so on obstructs smooth rotation of the rotation portion 3-5 and deprives the function of the erector, the maintenance and the inspection at predetermined times are necessary.
(3) Since the rotation of the gyro rotor 2 is led to the outside of the gyro casing 1, it becomes impossible to make the inside of the gyro casing 1 have a tightly-closed state so that dust and so on inevitably enter into the gyro casing 1, thus the life of the spin axis bearing are made short.
(4) Since the ball 3-15 which is heavy is rotated, the periodical torque acts so that even in the state in which the spin axis of the gyro rotor 2 becomes coincident with the vertical line, the spin axis is never completely made still but continues to conically rotate with a small conical angle (precession). That is, this conical movement of the spin axis becomes the error of the gyroscopic horizon.
(5) Due to the rotation friction caused between the ball 3-15 and the groove portion 1-1, when the inclination angle .theta. of the gyro casing 1 is small, a dead zone is produced by the gravity acting on the ball 3-15 so that the correct erection torque can not be produced.